Chelsea knew Derby County were going to be no pushovers in the Carabao Cup this week.
The Rams had impressively defeated Manchester United in the previous round, overcoming a 1-0 deficit before eventually progressing in a penalty shootout.
Not only that, but the Championship side entered Stamford Bridge under the management of Frank Lampard, who was always going to be pumped up for his return to the club.
And Derby certainly showed their potential to cause an upset, even if they made life hard for themselves with no less than two own goals in the first 45 minutes.
Chelsea loanee Fikayo Tomori put through his own net during the opening exchanges, but had his blushes spared by Jack Marriott who drew the game level.
Chelsea vs Derby
Another cross from Davide Zappacosta created another own goal, though, with Richard Keogh making the error and Martyn Waghorn proving the next Derby man to respond.
However, the key goal finally came a Chelsea player when Cesc Fabregas found the net with his first strike at Stamford Bridge since August 2017.
Across the midfield there was an opportunity to impress for Mateo Kovacic who has been competing with Ruben Loftus-Cheek and Ross Barkley this season.
Chelsea fans react to Kovacic
Both of his English teammates have been in fine goal-scoring form recently - bagging six strikes in the last three games - and Kovacic needed to impress to make the team.
And amid all the drama of the Derby game, Chelsea fans were impressed with his performance but just didn't see enough in his shooting to add that extra element to his game.
Supporters were egging him on to shoot during the match and when Kovacic obliged, he didn't look like scoring. Check out the reaction of fans on Twitter:
Is Kovacic a great player? 100% and Chelsea fans know it.
But goals win games and at the moment, his two rivals for that position are finding the net more regularly and Kovacic's overall goalscoring record is very poor.
He only scored three goals across his time with Real Madrid and Maurizio Sarri will need all the midfield efforts he can find with Jorginho and N'Golo Kante also in the side.
Kovacic is unlikely to be in the most competitive position in the whole Chelsea side and he might need an eye for goal to make it his.
When the margins are so small at Chelsea right now, individual attributes are key and there's no competing when it comes to goals.
Sorry Mateo, Chelsea fans want to make it work but you need that breakthrough strike.
Who do you think Sarri should start - Kovacic, Barkley or Loftus-Cheek? Have your say in the comments section below.